I have a Sony AVCHD camcorder that I don't always keep at home. I was wondering if there was a way for me to make a copy of its hard drive that I could use with iMovie.
There is. And you have a few options.
The most obvious option is to simply import everything on the camcorder's hard drive into iMovie. Neat. Clean. Done.
You can also create a duplicate copy of that camcorder's hard drive by launching Disk Utility (found in /Applications/Utilities), selecting it in the list of drives and volumes on the left side of the Disk Utility window, and choosing File -> New -> Disk Image From disknumber (where disknumber is the name give to the selected disk). In the resulting sheet choose Read/Write from the Image Format pop-up menu, None from the Encryption pop-up menu, and click the Save button.
Disk Utility will set about creating a disk image file of the camcorder's media drive. Once it finishes, you can unmount the camcorder's drive and disconnect the camera. When you'd like access to the camcorder's media (as saved when you created the disk image file), launch iMovie and double-click on the disk image file. It will mount and iMovie will behave as if you've plugged in your camcorder.
Unlike Final Cut Express and Final Cut Pro, iMovie won't allow you to directly import the .mts HD clips stored on the camcorder. However, you can make these clips accessible by wrapping or converting them.
Wrapping them entails demuxing the AVCHD content and shoving it into a .mov wrapper, which iMovie will import and convert to the AIC format. If that last sentence sounded like so much "Hubba dubba muxa foo" to you, don't sweat it. Divergent Media's $50 (approx. £32) ClipWrap does this. Just drag your .mts clips into the ClipWrap window, select Rewrap in the Output Format pop-up menu, and click Convert. You don't lose any of the quality of the original HD video in the process. (ClipWrap can also convert to other formats, AIC included.)
Another option is ShedWorx's $40 (approx. £26) VoltaicHD. This is a conversion utility that turns these .mts files into AIC QuickTime movies. iMovie is more than happy to import these movies.